1. Field of the Invention
The present invention relates to a stamper replacement method adopted in a vertical-type optical disk molding apparatus, by which replacement of a stamper for use in molding an optical disk is performed from outside of a mold on a stamper replacement member basis. The invention also relates to a mold for forming an optical disk.
2. Description of Related Art
Conventionally, in a case where a stamper for use in molding an optical disk such as a CD (compact disc) is directly fitted to a stamper fitting surface of a mold for forming an optical disk, replacement of the stamper has been performed in the interior of the mold. In this case, since the stamper fitting surface, formed as a mirror-finished surface, is likely to sustain a scratch, due care needs to be taken during the operation. Moreover, it is difficult to remove foreign matters, such as dust, entrained in between the stamper and the stamper fitting surface. Thus, after the stamper is fitted to the stamper fitting surface, the quality needs to be checked by performing trial pressing operation. Since stamper replacement, trial pressing, and other operations require much time, there are prepared in advance a multiplicity of stamper replacement units, each of which is constituted by pre-fitting a stamper with a stamper fitting surface. These stamper replacement units, after being subjected to a quality check by trial pressing, are attached to the mold for forming an optical disk. In this way, the stamper replacement operation is performed in an off-line mode.
FIG. 5 is an exploded side sectional view of a mold for forming an optical disk employed in a conventional vertical-type molding apparatus, in which stamper replacement is performed in accordance with the above-described manner. The mold includes a stamper replacement unit 1, a movable mold 2 to which the stamper replacement unit 1 is attached, and a fixed mold 3.
In FIG. 5, the stamper replacement unit 1 is constituted as follows. A stamper 6 is placed on a mirror-finished stamper fitting surface 5 of a mirror insert 4 arranged opposite to the fixed mold 3. The stamper 6 has its central part fixed to the mirror insert 4 by a stamper holder 7, and has its periphery fixed to the same by a peripheral ring 8. At the periphery of the stamper replacement unit 1 is attached a rotary ring 9 for fitting the unit 1 to the movable and fixed molds 2 and 3. The movable mold 2 includes a mirror insert 10 which has its surface facing the stamper 6 formed as a mirror-finished surface. The mirror insert 10 has a bolt 11 implanted at the periphery thereof, the bolt which is engaged with the rotary ring 9 to attach the stamper replacement unit 1 to the movable mold 2. The fixed mold 3 includes a plate 12 having a bolt 13 implanted at the periphery thereof. The bolt 13 is engaged with the rotary ring 9 to attach the stamper replacement unit 1 to the fixed mold 3.
The mold for forming an optical disk thus constituted is used as follows. Firstly, the stamper replacement unit 1 is manually attached to the movable mold 2 and placed in position. Subsequently, the movable and fixed molds 2 and 3 are closed, and the rotary ring 9 attached to the stamper replacement unit 1 is driven to rotate, so as for the bolt 13 of the fixed mold 3 to engage in an engagement hole of the rotary ring 9. Thereby, the stamper replacement unit 1 is attached to the fixed mold 3. Lastly, the bolt 13 is fastened using a wrench, at its side facing the parting surface of the fixed mold 3. Hereupon, attachment of the stamper to the fixed mold 3 is completed.
However, the conventional stamper replacement method and mold for forming an optical disk described above have the following disadvantages. Since the stamper replacement unit is manually attached to the mold in the interior of the mold by a worker, there is a possibility that the stamper replacement unit is attached to the mold in a slanting state inadvertently, or that the mirror-finished surface of the mirror insert of the movable mold sustains a scratch. Hence, the worker is required to carry out the manual operation with considerable care, and therefore a great deal of time needs to be spent in replacing the stamper.
The present invention has been devised in light of the above-mentioned problems, and accordingly its object is to provide a stamper replacement method and a mold for forming an optical disk employed in a vertical-type molding apparatus, by which a stamper replacement unit is attached to a mold from the outside of the mold, and a stamper is replaced with ease in a short period of time.
To achieve the above object, according to one aspect of the present invention, there is provided a stamper replacement method including the steps of: placing a stamper replacement unit, which has a stamper pre-mounted therein, on a movable mold; performing clamping in between the movable mold and a fixed mold; and fixedly attaching the stamper replacement unit to the fixed mold by: operating a single driving lever externally of the mold to drive two pieces of cam plates to slide within a groove provided in the fixed mold, the cam plates being attached to the driving lever in a shape of a letter xe2x80x9cCxe2x80x9d; and fastening fixing bolts by the cam plates, the fixing bolts being piercingly provided at symmetrically opposed four locations in the stamper replacement unit and the fixed mold stacked together.
According to another aspect of the invention, there is provided a mold for forming an optical disk including: a stamper replacement unit having a stamper pre-mounted therein; a movable mold; a fixed mold; fixing bolts piercingly provided at symmetrically opposed four locations in the stamper replacement unit and the fixed mold stacked together, the bolts for fixing the stamper replacement unit to the fixed mold; two pieces of cam plates including: a rack for rotating a screw portion of the bolt by threadedly engaging with the screw portion; and a tapered face for pushing the bolt upward so as for the stamper replacement unit to be clamp-fixed to the fixed mold; and a single driving lever for operating the two cam plates externally of the mold.
While novel features of the invention are set forth in the preceding, the invention, both as to organization and content, can be further understood and appreciated, along with other objects and features thereof, from the following detailed description and examples when taken in conjunction with the attached drawings.